A person that possesses both male and female characteristics to the extent that it can be hard to tell if they are a guy or a girl. Definitely looks better on guys than on girls for the most part, as many androgynous/effeminate men are considered attractive to the opposite sex. However, females that are androgynous can not pull it off nearly as well because.. well, come on, butch women are gross.
Justin Bieber is highly androgynous, as well as the lead singer of Tokyo Hotel.